1. Field of the Invention
The present invention relates to a nonreciprocal circuit device using a dielectric wave guide, a dielectric wave guide device incorporating the nonreciprocal circuit device, and a radio device using the dielectric wave guide device.
2. Description of the Related Art
A conventional circulator using a nonradiative dielectric wave guide (hereinafter an "NRD guide") has been described in Electronic Data Communications Academy Bulletin EMCJ92-54, MW92-94 (1992-10) "60 GHz Band NRD Guide Gunn Oscillator," and Electronic Data Communications Academy Research Papers C-I, Vol. J77-C-I, No. 11, pp. 592-598, November 1994, "60 GHz Band FM Gunn Oscillator using an NRD Guide".
FIG. 9 shows a conventional configuration of a circulator using the above NRD circuit. In FIG. 9, three dielectric strips 3, 4 and 5 are provided between two conductive plates 1 and 2 to form an NRD guide, and ferrite plates 6 and 7 are provided at the portion where these three dielectric strips join. Then, magnets 8 and 9 are provided so as to sandwich the ferrite plates 6 and 7 from outside the conductive plates 1 and 2.
A ferrite resonator comprising the ferrite plates 6 and 7 is excited by an electromagnetic wave which is transmitted through the dielectric strips. A DC magnetic field is applied vertically to the surfaces of the ferrite plates 6 and 7. At this time, due to the ferromagnetic characteristics of the ferrite plates, the permeability of the ferrite plates differs depending on the direction in which the high-frequency magnetic field rotates, and as a result the polarized wave faces rotate, functioning as a circulator.
However, in the conventional circulator using an NRD guide shown in FIG. 9, the DC magnetic field is not applied efficiently to the ferrite plates, since only single-body magnets are provided for this purpose. Furthermore, leakage of the magnetic field from the single-body magnets affects the other components, and when other magnetic bodies are nearby, there is a possibility that the DC magnetic field applied to the ferrite plates may be affected and varied adversely.
It has been considered to include a closed magnetic circuit of the type used in a circulator for the microwave band (without an NRD guide), in the circulator for the millimeter wave band using an NRD guide as described above. However, the NRD guide presents special problems. That is because an NRD guide has a particular configuration wherein a dielectric strip, used as a transmission line, passes between upper and lower conductive plates, and consequently steps must be taken to ensure that the electrical field of the dielectric strip is not affected. Therefore, the conventional closed magnetic circuit that is used in the conventional circulator in the microwave band cannot be used together with the NRD guide without alteration.